<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="author" content="http://www.softwhy.com/" />
<title>蚂蚁部落</title>
<script type="text/javascript">
var visaPrefixList = new Array(
 "4539",
 "4556",
 "4916",
 "4532",
 "4929",
 "40240071",
 "4485",
 "4716",
 "4"
);
var mastercardPrefixList = new Array(
 "51",
 "52",
 "53",
 "54",
 "55"
);
var amexPrefixList = new Array(
 "34",
 "37"
);
var discoverPrefixList = new Array("6011");
var dinersPrefixList = new Array(
 "300",
 "301",
 "302",
 "303",
 "36",
 "38"
);
var enRoutePrefixList = new Array(
 "2014",
 "2149"
);
var jcbPrefixList = new Array(
 "35"
);
var voyagerPrefixList = new Array("8699");
function strrev(str) {
  if (!str) return '';
  var revstr='';
  for (i = str.length-1; i>=0; i--)
   revstr+=str.charAt(i)
  return revstr;
}
/*
'prefix' is the start of the CC number as a string, 
any number of digits.
'length' is the length of the CC number to generate. 
Typically 13 or 16
*/
function completed_number(prefix, length) {
 var ccnumber = prefix;
 // generate digits
 while ( ccnumber.length < (length - 1) ) {
  ccnumber += Math.floor(Math.random()*10);
 }
 // reverse number and convert to int
 var reversedCCnumberString = strrev( ccnumber );
 var reversedCCnumber = new Array();
 for ( var i=0; i < reversedCCnumberString.length; i++ ) {
  reversedCCnumber[i] = parseInt(reversedCCnumberString.charAt(i));
 }
 // calculate sum
 var sum = 0;
 var pos = 0;
 while ( pos < length - 1 ) {
  odd = reversedCCnumber[ pos ] * 2;
  if ( odd > 9 ) {
   odd -= 9;
  }
  sum += odd;
  if ( pos != (length - 2) ) {
    
   sum += reversedCCnumber[ pos +1 ];
  }
  pos += 2;
 }
 // calculate check digit
 var checkdigit = ((Math.floor(sum/10)+1)*10-sum)%10;
 ccnumber += checkdigit;
 return ccnumber;
}
function credit_card_number(prefixList, length, howMany) {
 var result = new Array();
 for (var i = 0; i < howMany; i++) {
  var randomArrayIndex = Math.floor(Math.random() * 
 prefixList.length);
  var ccnumber = prefixList[ randomArrayIndex ];
  result.push( completed_number(ccnumber, length) );
 }
 return result;
}
window.onload=function(){
  var visa = credit_card_number(visaPrefixList, 16, 3);
  var amex = credit_card_number(amexPrefixList, 15, 3);
  var obox=document.getElementById("box");
  var lis=obox.getElementsByTagName("li");
  lis[0].innerHTML="visa:"+visa;
  lis[1].innerHTML="amex:"+amex;
}
</script>
</head>
<body>
  <ul id="box">
    <li></li>
    <li></li>
  </ul>
</body>
</HTML>